The invention relates to an ultrasonic method and means for removing an osteal prosthesis from cemented installation in a living bone, as in the course of revision arthroplasty.
It is known from U.S. Pat. Nos. 4,248,232 and 5,151,099 that ultrasound may be used to facilitate removal of bone cement (PMMA) during revision arthroplasty. Local heating, by preferential absorption of ultrasound energy, raises the temperature of a small volume of the cement above the glasstransition temperature, thus allowing the cement to flow and to be manipulated into a shape and form which may be readily removed from the revision site.
It has also been claimed (Hood, et al., U.S. Pat. No. 5,045,054) that the application of ultrasound directly to the prosthesis can break the bond between the prosthesis and surrounding cement or, in the case of uncemented prostheses, between the prosthesis and in-grown cancellous bone. The direction of applied ultrasonic energy is in line with the central axis of an implanted prosthetic device, such as the axis of stem support for the ball of a hip-joint replacement. But the in-line application of force, as in the context of the Hood, et al. system, is to require the patient to oppose the force, with inevitable trauma for the patient.